Rotary valve fob steam-engines



UNITED STATES PATENT OFFICE.

THOS. STEWART, OF PHILADELPHIA, PENNSYLVANIA.

ROTARY VALVE FOR STEAM-ENGINES.

Specification of Letters Patent No. 21,579, dated September 21, 1858.

T 0 all whom t may concern.'

Be it known that I, THOMAS STEWART, of the city of Philadelphia, in theState of Pennsylvania, have invented a new and Improved Rotary Cut-OffValve for Steam- Engines; and I do hereby declare that the following isa full, clear, and exact description of the construction and operationof the same, reference being had to the accompanying drawings, making apart of this specification, in whichd Figure 1 is a plan view of thecut-off and valve as applied to the middle of the cylinder of an engine,the cap of the steam chest being removed; Fig. 2, a vertical transversesection through the middle of the same; Fig. 3, a plan view of the underside ofthe valve disk; and Figs. 4, and 6, sectional representations ofactuating parts of the cut-offlike letters in the different iiguresindicating the same objects.

The nature of my invention consists in making the disk of a rotaryvalve, with two or more sets of ports or steam ways therein, for theinduction and eduction of the steam, in such a manner as to allow of thesaid steam being cut oi" at any required position of the piston in thecylinder without producing any connection with the opposite side of thesaid piston when the steam is cut short oif and in so constructing andoperating the cut-olf as to cause it to work independently of the saidvalve.

Referring to the drawings, A, is the rotary valve; B, the cut-oif and C,the valveseat, or bottom of the steam chest. The valve-seat is cast withthe cylinder, D, and has its ports leading therefrom into the respectiveends of the cylinder, as shown by the red lines in Fig. l, and also witha boss or mass of metal, C', projecting down from the middle of theunder side of the same which, being bored, receives the stem A', of thevalve A) ,and also affords the exhaustway gt as shown by the red linesin Fig. 2. The stem A', of the valve (A) is also bored and receives thestem B, of the cut-01T. The two ports through the valve-seat which openinto the cylinder (D) are indicated by the red lines e and e in Fig. l;and in the saine figure, the supply ports f f2, f3, of the valve (A) areindicated in blue lines; but these ports, as also the exhaust ports orways, g', g2, g3, are more fully shown in Figs. 2 and 3.

L, and h2, are the ports in the cut-off, and,

h3, the entrance opening -in the cap of the steam chest.

I, is a bevel wheel which is fast on the lower end of the valve stem(A), and into which gears a bevel pinion, K, which is fixed on the innerend of a shaft, L, which connects, by a pair of bevel wheels with thecrank shaft M. The stem (B) of the cut off projects through the stem ofthe valve (A) and has an equal-armed lever, N, fixed thereon. Parallelwith the steam cylinder (D), a shaft, O, having two cylinders, P and P,and a spur wheel, Q, fixed thereon, is connected by the pinions, R3 andS3, with the shaft so as to be rotated thereby. These cylinders are eachsurrounded with a thin, metallic, spring-band, R and R, which has itstwo ends jointed to a lever, S, so that when t-he said lever isoperated, the band can be made to clutch upon` the cylinder so as to becarried thereby. The lower or inner ends of these bands (R and R) areconnected by a chain or wire rope T and T', respectively with the armsof the horizontal lever (N), while the power-ends of each of the levers,S and S', are connected by a like chain or wire rope, respectively tothe ends of an equal-armed lever, U, which is placed above and so as tobe vibrated upon its fulcrum, by means of a lever connecting it at, W,with the usual governor of the steam engine. The cut-Gif (B) isadjustable vertically by means of the two set screws V and V. The gearwheels for giving motion to the valve (A) are made so as to cause thelatter to make one third of a rotation for every full rotation of thecrank shaft (M), and are arranged relatively so as to cause the valve tocommence opening the ports to the cylinder as the crank passes f thedead point.

Operation: When steam is admitted into the valve chest and suicientrotation given to the crank shaft to open either port, the steam wouldafterward continue to be admitted and exhausted alternately to and fromeach side of the piston; but the cutoi (B) being previously arranged inconnection with the usual governor so as to cut off the steam at anyrequired position of the piston, it is obvious that any irregularity inthe speed of the engine will instantly be communicated to the saidgovernor through the media of the lever (U) and either the one or theother of the cylinders (R, R) connected therewith so as to cause thecylinder carrying the friction clutch to draw on the lever (N) and thuspartially to rotate the cut-oft1 and so regulate the ,size of theopening for the steam, to suit the re quirements of the engine, becausethe cylinders (P and P) being always rotating in the direction of thearrow it is'manifest that when one of the friction clutches is caused bythe governor to graspits cylinder, the other, by the same motion of thegovernor, is caused to release the other cylinder until the cut-off issuiiciently turned by the cylinder to produce the equalization requiredin the speed of the engine; while at the same time, the cut-oif beingadjustable vertically upon the valve (A) by means of the set screws (Vand V) the valve can thereby be packed or balanced so as to diminish thefriction very materially, and thus save power without allowing steam topass between their faces.

The arrangement of the openings or ports of the valve (A) as described,allows of the steam being cut 0E at any required position of the pistonwithout producing any co-nnection with the opposite side of the saidpiston; and hencethe action of the cut-off upon the valve may be termeduniversalthe two being adapted together so as to admit, cut otf, andwork the steam expansively and exclusively on either side of the pistonat any position of the same in the cylinder. Besides, the constructionand arrangement of the several .parts are simple, inexpensive, and notliable to get out of order from use.

f Having thus fully described the construction and operation of myinvention I proceed to state that I dovnot claim generally, a rotaryvalve for the induction and efducn tion of steam; neither do I claimgenerally,

mounting an independent cut-off upon the upper side of a'valve'; but y YWhat I claim as my invention and desire to secure by Letters Patent isl.I claim making a rotary valve with an independent cut-oli' appliedthereto, constructed, arranged andv operating substantially in themannerk herein set forth.

2. I claim constructing the said rotary valve with two or more sets ofports or ways therein as described for theinduction and eduction of thesteam, so as to enable me to cut off the said steam at any required partof the stroke without producing any connection with the opposite side ofthe piston, when the steam is cut ofi"r short as set forth anddescribed.

THOS. STEWART.

